In a 3G mobile communication system, the software entity of UP (User Plane, a plane for transmitting user data) protocol generally exists in an MGM (Media Gateway), an RNC (Radio Network Controller) of UTRAN (UMTS Terrestrial Radio Access Network). The Iu Interface is an interface between a Radio Access Network and a Core Network, and the Nb Interface is an interface between Media Gateways. The two objects of IuUP/NbUP protocol includes: (1) transmitting UP data, guaranteeing the QoS (Quality of Service) of UP data transmission through the UP control signaling (UP initialization, rate control, time alignment and error event Indicator); (2) keeping the independence of the CN (Core Network), thus reducing the dependence of the CN on the Transfer Network Layer (TNL), e.g. RTP/UDP/IP, as far as possible.
An existing technical solution of IuUP/NbUP procedure control is shown in FIG. 1. An UP frame checking and distributing module 101 checks the UP frame number, performs CRC (Cyclic Redundancy Check) for the UP frames received by the system, and differentiates the data frames and the control frames depending on the PDUType (Pritocol data unit type) in the UP frame header. At present, only an SMpSDU (Support mode for predefined SDU size, SMpSDU) support mode is defined in the UP protocols of 3G standard (3GPP TS 25.415, 3GPP TS 29.415). Under the SMpSDU support mode, the PDUType value of a data frame is 0 or 1, while the PDUType value of a control frame is 14. The UP frame checking and distributing module 101 determines whether a received UP frame is a control frame or a data frame according to the PDUType value of this UP frame. If it is a control frame, the UP frame checking and distributing module 101 transmits it to an UP request-frame distributing/response-frame packaging and transmitting module 102, and if it is a data frame, the UP frame checking and distributing module 101 transmits it to a data frame processing module 108.
On receiving the control frame, the UP request-frame distributing/response-frame packaging and transmitting module 102 determines the type of the control frame depending on the Procedure Indicator in the frame header, and distributes the control frame to the corresponding procedure control module according to the type of the control frame. The procedure control module may be an UP initialization processing module 103, an UP time alignment processing module 104, an UP rate control processing module 105 and an UP error event processing module 106. The processing procedure of each module will be described hereinafter. On receiving the control frame, if the UP request-frame distributing/response-frame packaging and transmitting module 102 determines the control frame is an initialization frame, the UP request-frame distributing/response-frame packaging and transmitting module 102 transmits it to the UP initialization processing module 103. If the control frame is determined to be a rate control request frame, the UP request-frame distributing/response-frame packaging and transmitting module 102 transmits it to the UP rate control processing module 105. If the control frame is determined to be a time alignment request frame, the UP request-frame distributing/response-frame packaging and transmitting module 102 transmits it to the UP time alignment processing module 104. The processing procedure of the modules will be described below.
On receiving the initialization frame, the UP initialization processing module 103 extracts a set of RFCIs (RFCI: Radio Access Bearer Sub-flow Combination Indicators) supported by the sender and the length of the bearer sub-flow service data unit (SDU) corresponding to each set of RFCIs. Thereafter, according to the set of RFCIs, the data stream processing entity will be controlled to transmit and receive the UP data streams.
On receiving the rate control request frame of a control originator, the UP rate control processing module 105 extracts the maximal rate demanded by the control originator, and then transmits the rate control message to the TC encoding/decoding channel, indicating the TC encoding/decoding channel to adjust the transmitting rate of the data frame to a predefined value. After a successful rate adjustment, the UP rate control processing module transmits a response frame to the control originator.
On receiving the time alignment request frame from the control originator, the UP time alignment processing module 104 extracts the time alignment value, and then transmits a time control message to the TC encoding/decoding channel, indicating the TC encoding/decoding channel to advance or postpone the transmitting time of the data frame by the predefined value. After a successful time alignment, the UP time alignment processing module transmits a response frame to the control originator.
When an error is found in the procedure for processing the data frame or the control frame, the UP error event processing module 108 will be informed. Upon the determination of the type of the error, the UP error event processing module 108 transmits an error event frame to the entity of the opposite end. As for the error event frame transmitted from the opposite end, the local end will record the event and inform the data-stream processing function entity to handle accordingly.
It can be seen from the above described technical solution of IUUP/NBUP procedure control that, during the procedure control, the operation of the execution entity of procedure control function, i.e. the TC encoding/decoding channel 107, by the processing modules is asynchronous and monopolized. That is, the next operation request can not be executed before the previous operation request is ended. For example, on receiving a rate control request frame, the UP rate control processing module 105 transmits a rate control message to the TC encoding/decoding channel 107, and the system also receives a time alignment request frame before the TC encoding/decoding channel 107 returns a response. Then the latter time alignment request will be suspended for the TC encoding/decoding channel 107 is processing the previous rate control request. According to the UP protocol of 3G standard (3GPP TS 25.415), in an UP support mode session, UP initialization is the first UP procedure control function, after which, the UP rate control processing module, the UP time alignment processing module and the UP error event processing module are all independent from each other, and cannot be restricted by each other when implementing the procedure control function.
For the processing of multiple successive rate control requests, according to the UP protocols of 3G standard, when the system receives multiple rate control request frames successively, the final rate control will be adopted. Thus, in this solution, only the first rate request will be processed normally, the next rate control request may be dropped. As a result, it is possible that the frame number in the response frame received by the rate control sender does not match with the frame number in the finally transmitted rate control frame, resulting in the failure of the final rate control.
This solution can process only the procedure control after the receipt of an UP control request, it does not support the origination of UP initialization, UP time alignment and UP rate control. According to the UP protocols of 3G standard, both of a RNC and a NGW may be not only an originator but also a handler of the UP control operations. When the RNC and MGW are the handlers of the UP control operation, it is impossible to implement the UP procedure control.
This solution supports only the procedure control processing under SMpSDU support mode. As the UP checking and distributing module does not differentiate the support modes when the UP frames are received, It is necessary to modify the software considerately when two versions of UP support modes need to be supported simultaneously.